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Andesite (Holocene and Pleistocene)

Forms major stratovolcanoes dominantly of aphyric to porphyritic basaltic andesite and andesite; phenocrysts are principally pyroxene, olivine, plagioclase, and, rarely, hornblende. Locally includes dacite and minor basalt
StateOregon
NameAndesite (Holocene and Pleistocene)
Geologic ageQuaternary
Original map labelQa
Commentsstratocones
Primary rock typebasalt
Secondary rock typeandesite
Other rock typesdacite
Lithologic constituents
Major
Igneous > Volcanic > Mafic-volcanic > Andesite (Flow)
Igneous > Volcanic > Mafic-volcanic > Basaltic-andesite (Flow)
Incidental
Igneous > Volcanic > Mafic-volcanic > Basalt (Flow)
Igneous > Volcanic > Felsic-volcanic > Dacite (Flow)
Map references
Walker, G.W. and MacLeod, N.S., 1991, Geologic map of Oregon: U.S. Geological Survey, scale 1:500,000.
Unit references
Walker, G.W. and MacLeod, N.S., 1991, Geologic map of Oregon: U.S. Geological Survey, scale 1:500,000.
Geographic coverageBaker - Clackamas - Deschutes - Douglas - Hood River - Jackson - Jefferson - Klamath - Lane - Linn - Marion

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